Electrical impedance unit



NOV 18, 1952 E. c. ALTENBr-:RGER

ELECTRICALMPEDANCE UNIT Filed Feb. 25, 1950 vlu,

L S ATTORNEYS ltvatentecl Nov. i8, 149522 ELECTRICAL IMPEDANCE UNITEdmund C. Altenbergcr, Plainfield, N. J., assignor to Essex Electronics,a corporation of New Jersey Application February 25, 1950, Serial No.146,267

4 Claims.

This invention relates to an adjustable capacitor and more particularlyto an adjustable capacitor for varying the coupling inv a capacitycoupled radio-frequency transformer unit.

Where capacitative coupling is employed between the primary andsecondary of radio-frequency transformer units, which require the shieldor can in which the transformer is enclosed, to be opened in order forthe capacitor to be adjusted, properly to tune the circuit in which thetransformer is used, such adjustment is time consuming 1in that itrequires the can to be removed for each adjustment and in addition asthe characteristics of the circuit will change when such can is removed,an adjustment made under such conditions may not be correct when the canis restored for normal operation.

Where conventional trimmer capacitors of the type using movable platesare employed for such capacitative coupling, in addition to therelatively high cost of such capacitors in relation to the cost of theother components used in the unit, the unit must be made of larger sizein order to accommodate such capacitor and where many radio frequencytransformers are used, as in a radio receiver, the overall increase insize of the receiver unit may be objectionable, especially when suchreceivers are used in small, compact devices such as guided missiles orthe like.

It is accordingly among the objects of the invention to provide acapacitor that may be incorporated in a radio-frequency transformer unitwithout any material increase in the size or cost thereof and which mayreadily be adjusted properly to tune the circuit without opening the canin which the transformer is housed.

' prises a substantially tubular body of dielectric material with aconductive metallic outer surface as one electrode and a conductivemetallic element, extending longitudinally with small clearance in thebore of the body and adjustable lengthwise thereof, as the otherelectrode. Preferably the metallic element in the bore of said tubularbody is a wire protruding from one end of such bore, and the metallicouter surface of said tubular body is desirably a conductive coating,whereby when the length of wire in the bore of the tubular body isvaried the value of the capacitance will be correspondingly changed.

In a specific embodiment herein shown to illustrate the invention, thetubular body is desirably mounted on the base of a radio-frequencytransformer, preferably extending laterally of the coil form of saidtransformer, with the end of the wire which extends from said tubularbody being aflixed to one of the terminal lugs of the unit.

In the accompanying drawings in which is shown one of various possibleembodiments of the several features of the invention,

Fig. l is a perspective view of a radio frequency transformerincorporating the present invention,

Fig. 2 is a longitudinal sectional view taken along line 2-2 of Fig. l,

Fig. 3 is a transverse sectional view taken along line 3-3 of Fig. 2,and

Fig. 4 is a view similar to Fig. 3 of another embodiment of theinvention.

Referring now to the drawings, a metal can or shield I0 is affixed atits rim in conventional manner about a base I I of insulating material,such as Bakelite upon which the radio frequency transformer unit ismounted. The base illustratively has four terminal lugs I2, one at eachcorner thereof and desirably protruding beyond the under and upper facethereof. An upstanding coil form I3 is mounted on the base II andillustratively has two coils I4 and I5 wound thereon.

The transformer is desirably resistance loaded in the illustrativeembodiment shown herein, by means of a pair of resistors I6 and I1, theterminals I8 and i9 of each of which are affixed to the upper protrudingends of the pair of terminal lugs I2 to which the ends of coils I4 andI5 respectively are also affixed.

To provide for capacitative coupling between coils I 4 and I5 acapacitor unit 2| is provided which is adjustable in order that thecircuit in which the transformer is used may be tuned.

According to the invention the capacitor unit 2I as shown in thedrawings desirably comprises a tube 22 of dielectric material such asceramic, having a metallic element or electrode 23 on the outer surfacethereof desirably a coating of conductive metallic paint as shown inFigs. 1 to 3. or, if desired, instead of a coating of metallic paint, ametal sleeve 23 could be used as shown in Fig. 4. Tube 22 is preferablya'ixed in a vertical bore 24 in base II so as to be securely retainedtherein with the lower end of the tube desirably substantially flushwith the under surface of the base I I and with the upper portion of thetube extending above the surface of base II laterally of coil form I3.

A metallic element or electrode, desirably a wire 25, is positioned inthe bore of said tube 22 so as to be adjustable lengthwise thereof. Thediameter of said bore is desirably only slightly greater than thediameter of said wire so as to provide but slight clearance therebetweenand one end of said wire extends from the lower end of said bore. Theouter extremity of said wire is affixed as by soldering as at 26 to oneof the terminal lugs I2, illustratively the terminal lug to which one ofthe ends of coil I5 is axed. Preferably the portion of Wire 25 extendingfrom tube 22 is reversely bent as at 21 to provide sufcient length ofwire to permit movement thereof into the bore of said tube.

In order to complete the circuit, the metallic element 23 or 23 on theouter surface of tube '22, preferably at the upper end thereof, has alead 28 aixed thereto as by soldering, with the free end 29 of said leadconnected to one of the terminal lugs I2 to which one of the ends ofcoil I4 is also affixed.

After the assembled transformer unit is installed in conventional manneron the chassis of a radio receiver or other device in which it is to beused, it may readily and quickly be tuned from the under side of thechassis without removal of the can I0, by moving the lead 25 withrespect to the bore of the tube 22 so that more or less of the lead iswithin such bore. Thus the elfective capacitance of the condenser unit2I will be varied to tune the circuit and a drop of cement 32 may beplaced on the lower end of the tube securely to retain the lead in itsfixed selected position therein when the transformer is properly tuned.

It is to be noted that if the can I9 must be removed for the tuningoperation, as the characteristics of the circuit would be diiferent whenthe can was restored, although the circuit may be tuned with the canremoved when such can is replaced the circuit might again be out oftune. This difficulty is avoided by the arrangement and construction ofthe unit herein described.

As many changes could be made in the above construction and manyapparently widely different embodiments of this invention could be madewithout departing from the scope of the claims, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingrsense.

Having thus described my invention what I claim as new and desire tosecure by Letters Patent of the United States is:

1. A radio frequency transformer comprising a base, a coil form mountedon said base, a pair of coils wound about said form, a tubular body ofdielectric material mounted on said base extending laterally of saidcoil form with the upper portion of said tubular body extending abovethe upper face of said base, said tubular body having an electrode onthe outer surface thereof, a lead connecting said electrode to one ofsaid coils,

ISU

and a wire extending longitudinally in the bore of said tubular body andprotruding from the lower end thereof on the under surface of said baseand axed to a lead from the other of said coils, the diameter of saidbore being only slightly greater than the diameter of said wire toprovide but slight clearance therebetween thereby to afford slidingmovement of said wire in said bore.

2. The combination set forth in claim. 1 in which the portion of saidwire protruding from the end of said tubular body is of length to permitmovement of said wire into said bore.

3. The combination set forth in claim 1 in which said tubular bodyextends laterally of said coil form.

4. A radio frequency transformer comprising a base of insulatingmaterial, at least four contact lugs on said base, an upstanding coilform alxed at one end to said base, a pair of coils wound about saidform, the terminals of one of said coils being connected to one pair oflugs respectively and the terminals of the other of said coils beingconnected to the other pair of lugs respectively, a tubular body ofdielectric material mounted on said base extending laterally of saidcoil form with the upper portion of said tubular body extending abovethe upper surface of said base, said tubular body having an electrode onthe outer surface thereof, a lead connecting said metallic electrode toone of the lugs to which a terminal of one of said coils is affixed, awire extending longitudinally in the bore of said tubular body andprotruding from the lower end thereof on the under surface of said baseand affixed to the depending end of one of the lugs to which a terminalof the other of said coils is connected, the diameter of said bore beingonly slightly greater than the diameter of said wire to provide butslight clearance therebetween thereby to afford sliding movement of saidwire in said bore.

EDMUND C. ALTENBERGER.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS

